Brachytherapy is a form of cancer treatment in which radiation sources are placed inside a patient's body to irradiate a tumor. In brachytherapy, a surgeon usually implants several radioactive seeds in or around a tumor, thus providing a higher radiation dose to the tumor than would be possible with external beam radiation therapy. Careful placement of the radioactive seeds allows localized and precise irradiation of the tumor.
Radioactive seeds typically are very small (generally about 0.8 mm by 4.5 mm), roughly cylindrical objects containing very small amounts of radioactive material. Two radioactive isotopes commonly used for permanent implants are iodine-125, often used to treat slower growing tumors, and palladium-103, which is preferred when a tumor is fast growing. Other radioactive materials also can be used in implants.
Radioactive seeds for use in brachytherapy procedures typically are carried in and used from small containers such as seed cartridges that can be used with a delivery system (e.g., a brachytherapy applicator such as the Mick applicator). Alternatively, radioactive seeds can be packaged loose in small glass or plastic vials for later assembly into seed cartridges or brachytherapy needles. In either case, the radioactive seeds can be loaded into a seed cartridge and/or a brachytherapy applicator for delivery to the patient.